Extending the field-of-view of speckle-based microtomography with the UMPA model

Phase-contrast computed tomography enables the visualization of weakly-absorbing samples with high contrast. Speckle-based imaging (SBI) is a phase-sensitive X-ray imaging technique that requires the use of a wavefront marker (typically a sandpaper) to retrieve multi-modal information: absorption, refraction and scattering. These quantities are derived by analyzing the distortions in a reference pattern generated when the sample is inserted into the beam. The Unified Modulated Pattern Analysis (UMPA) model is a speckle-tracking method capable of processing such datasets. While high-resolution tomographic reconstructions can be achieved at the synchrotron, there is usually a trade-off with sample dimensions. Here, we use UMPA with a multi-frame approach for signal retrieval, enabling the expansion of the reconstructed field-of-view (FOV) by moving the sample instead of the modulator transversely to the beam. We demonstrate this technique on a human placental tissue sample.